The Kvarken Archipelago
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Template for Submission of Scientific Information to Describe Areas Meeting Scientific Criteria for Ecologically or Biologically Significant Marine Areas THE KVARKEN ARCHIPELAGO Abstract Kvarken is a narrow (26 km) strait between Sweden and Finland in the northern Baltic Sea. The proposed area encompasses a mosaic archipelago on the Finnish side, which consists of ca. 5600 islands and skerries. A large part of the area is a World Heritage site, which is characterized by its unique landscape formed during the last glaciation (10.000 – 8.000 BP), including large fields of De Geer moraines. The isostatic land uplift is still ongoing at a rate of 8 mm per year. The land uplift creates approx. 1 km2 new land each year and affects all underwater biotopes and habitats by constantly bringing new areas up into the photic zone. The relative latitudinal change in salinity is the largest in the Baltic Sea, and the area is a transition zone, where marine fauna and flora rapidly change into freshwater ones. E.g., the southern side is characterised by marine algae, while the species richness of aquatic vascular plants and charophytes (including rare species) is higher on the northern, less saline, side of the area. A large number of bird species nest or stop on their migration in the area. Introduction The Kvarken Archipelago exhibits a unique combination of characteristics that can be found nowhere else, which is also the basis for the World Heritage Site nomination. According to UNESCO, “the area affords outstanding opportunities for the understanding of the important processes that formed the glaciated and land uplift areas of the Earth's surface.” http://whc.unesco.org/en/list/898 The Kvarken Archipelago is located on the crystalline bedrock, which forms a unique, brackish shallow water marine environment with a number of moraines (Fig. 5 & 6). Especially the washboard- like De Geer moraines and boulder fields found both on terrestrial and submarine areas characterize the landscape of the Kvarken, and contribute to its high geodiversity (e.g. Breilin et al., 2004; Kaskela & Kotilainen, 2017; Kotilainen & Kaskela, 2017). The isostatic land uplift is still ongoing at a rate of 8 mm per year. The land uplift creates approx. 1 km2 new land each year. Combined with the ongoing land uplift, the moraines lead into succession of the elevated structures from the seafloor to land. The seabed of the shallow Kvarken Archipelago includes silt, sand and hard bottoms, often in a small- scale mosaic pattern. The geological formations create additional variation by affecting the exposure (from highly sheltered to highly exposed within a small spatial scale). Salinity in the area is low, from 3 to 5 psu, increasing towards the south (Fig. 8). The relative change in salinity per distance from the northern to the southern part of the area is the largest in the Baltic. Salinity also varies depending on variation of sea level on the two sides of Kvarken, and is affected by the outflow from the Bothnian Bay, which in turn depends on the river discharge into the Bothnian Bay. The consequent “river” flowing through the Kvarken has a yearly mean slightly above 3000 m3/s. As the Kvarken strait is both narrow and shallow, the outflow takes the form of an intermittent current which can reach a speed of several knots. The salinity is also affected by a counter clockwise current in the Bothnian Sea, which brings water with higher salinity into the Kvarken area from the south. The area is covered by annual sea ice (Fig. 10), but the number of ice days has been steadily declining in the open sea areas due to recent warming up of the climate (Haapala et al. 2015). Regular monitoring of the ecological state of the sea takes place in the area. The Finnish Inventory Programme for Marine Underwater Environment (VELMU) has conducted extensive biodiversity inventories in the area. The inventories done in 2004-2017 have included dive lines and drop videos, benthic sampling, fish larvae sampling, and echosoundings. Observation data for hundreds of species is available. Also, species distribution models (SDMs) have been made for many species (below FIN EBSA: The Kvarken Archipelago 1 referred to as “VELMU data”; viewable in https://paikkatieto.ymparisto.fi/velmu). Spatial data on birdlife and seals also exist. Location The Kvarken Archipelago (Fig. 1 & 2) is located in the Gulf of Bothnia, northern Baltic Sea. The total area of the proposed EBSA is 7151 km2 and its sea area is 6517 km2. The mean depth of the area is 21 m, with the deepest point in the open sea being 101 m (Fig. 7). The area is within the Finnish territorial waters, and is within national jurisdiction. Feature description of the proposed area The area encompasses a World Heritage Site, several Natura 2000 areas and Important Bird Areas (IBAs), as well as a Ramsar site (Fig. 11). The shallow area of the Kvarken Archipelago includes silt, sand and hard bottoms, often in a small- scale mosaic pattern due to a topography consisting of Ice Age formations. The geological formations create additional variation by affecting the exposure (from highly sheltered to highly exposed within a small spatial scale), in turn further generating comparatively high local biodiversity. Due to the low salinity (3 to 5 psu) and the steep salinity gradient (Fig. 8), the area is a transition zone zone between marine and freshwater fauna and flora. E.g., the northern side has a high diversity of aquatic vascular plants and charophytes (including rare species), while the southern side is characterised by algal communities (Fig. 18). Several marine species, for instance bladderwrack Fucus vesiculosus and the blue mussel Mytilus trossulus) reach their northernmost distribution in the Kvarken area. As in the rest of the Baltic Sea, there is a continuous evolutionary pressure on species to adapt along the salinity gradient (from fresh water to saline water and vice versa). The unique topography of the Kvarken area coupled with the land uplift facilitates this process by creating a multitude of variations (depth, substrate, exposure, salinity), all of which are under constant change. Of special importance is the flad-glo lake succession (a flad is a coastal lagoon), which transforms topographically enclosed sea areas into freshwater lakes (over a period of 200 years), usually forming a connected system of small water masses in different successional stages. Many flads and glo-lakes are biodiversity hotspots for vascular plants and charophytes. They are also important spawning areas for fish, as they warm up faster and earlier than the surrounding sea while at the same time offering a sheltered environment. The Kvarken area is productive, due to an overall shallowness and abundance of light (Fig. 9), as well as continuously changing water currents that transport nutrients and mix the water. The area is important for several fish species. Due to many flad bays it forms a very important reproduction area of perch (Perca fluviatilis) in Finland. This area is also an important corridor for migrating anadromous European whitefish (Coregonus lavaretus sl.), salmon (Salmo salar) and sea trout (Salmo trutta) (Kallio-Nyberg et al. 2017). Some of the most important breeding areas for archipelago birds in the Baltic are situated in the area, including the island groups of Norrskär, Valassaaret and Rönnskären. In the inner archipelago the global warming affects the thickness of the ice. This is of great importance for the ringed seal (Pusa hispida botnica), which depends on the annual ice for reproduction. FIN EBSA: The Kvarken Archipelago 2 Table 1. Number of species in different sea areas listed by HELCOM (HELCOM 2012). The total number of species in the Baltic Sea is 2730 of which 1898 species are invertebrates. Total number of species in the table excludes bird species. Gulf of Finland Archipelago Sea Kvarken Archipelago Bothnian Sea Macrophytes 187 68 162 116 Benthic invertebrates 482 122 96 132 Fish & lamprey 87 68 51 48 Marine mammals 3 3 2 2 Total number of species 759 261 311 298 Share of species in the Baltic Sea 27.8 % 9.6 % 11.4 % 10.9 % Feature condition and future outlook of the proposed area The naturalness of the area is high, due to low degree of building in the area, and short summer period when most of the tourism activities take place. The overall condition of the area is better than that of the more southern areas of the Baltic Sea, because the anthropogenic nutrient loading is intermediate, and the continuous movement of water flushes organic material towards the Bothnian Bay in the north and the Bothnian Sea in the south, alleviating the negative effects of nutrient loading in the area. North-south and east-west ship traffic concentrate in a narrow area due to the strait and cause some disturbance to the area. A wrecking of ships carrying oil or chemicals is a serious threat to this shallow archipelago area. Climate change will affect the effects of the ongoing land uplift as a result of sea level rise. While the isostatic rebound (land uplift) will continue at approximately the same speed (8 mm per year) and will eventually generate a topographic height increase of 140 meters (compared to today), an increasing sea level will counteract the process (Grinstedt, 2015), and slow down the natural succession of flads to freshwater and terrestrial environments. This will change the characteristics of the area from a biological and evolutionary viewpoint. FIN EBSA: The Kvarken Archipelago 3 Assessment of the area against CBD EBSA Criteria CBD EBSA Description Ranking of criterion relevance Criteria (Annex I to decision IX/20) (please mark one column with an X) (Annex I to No Low Medi High decision informat um IX/20) ion Uniqueness or Area contains either (i) unique (“the only one of rarity its kind”), rare (occurs only in few locations) or endemic species, populations or communities, X and/or (ii) unique, rare or distinct, habitats or ecosystems; and/or (iii) unique or unusual geomorphological or oceanographic features.